高色纯度有机白光电致发光器件

Tuning Chromaticity of White Organic Light-emitting Devices with a New Multilayer Structure

介绍了具有高色纯度的多层有机白光器件,器件发光的色坐标为x=0.33,y=0.34,非常接近白光等能点,是色度很好的白光器件。而且在8～14V很大的范围内,发光色度随器件的驱动电压或电流的变化不大,基本稳定在x=0.33,y=0.34。在电压为19V时,器件的亮度达到了最大9735cd/m2,在电压为9V时,器件的效率达到了最大4.5cd/A。

We have designed a device of new multi-layer structure and carried out the experiment on white light-emitting. In a white organic EL device with multi-layer, generally, white light emission can be obtained by blending blue emission and one or two others with long wavelength such as yellow, red or green emission. Because the energy band of material emitting blue light is broad and the efficiency of it is lower, how to raise the efficiency of blue emission from the white light-emitting device is the key of fabrication of a white organic light-emitting device with pure color, high efficiency and brightness. Therefore, we have designed the new structure of a device reasonably and increased the efficiency of blue light emission effectively and (conveniently). The new multi-layer structure of the device limits blue emission within a very narrow scope (between) hole and electron transport layer, and causes one part of majority holes injected in to be captured by rubrene to combine with electrons in the transport process for yellow emission, and the other part of them to (arrive) the thin layer of DPVBi for increasing blue emission, so raising the efficiency of white light emission (over) blending yellow and blue emission, and enhancing the whole function of the device. From the electroluminescence spectrum, it is found that only the DPVBi and rubrene could emit light but NPB and Alq_3 couldn't. This explains that all energy of Alq_3 is transported to DPVBi and rubrene. The structure of the device is ITO/NPB(35 nm)/DPVBi(4 nm)/Rubrene(0.1 nm)/Alq_3(6 nm)/NPB(5 nm)/DPVBi(4 nm)/Rubrene(0.1 nm)/Alq_3(6 nm)/NPB(5 nm)/DPVBi(4 nm)/Alq_3(35 nm)/LiF(0.5 nm)/Al(200 nm). The commission international De L'Eclariage (CIE) coordination of the devices is very stable at (0.33, 0.34) while the applied voltage varies from 8 V to 14 V. The maximum electroluminescence efficiency is 4.0 cd /A at 10 V. It may be deduced that the reason why the device can emit white light is that blue and yellow emission can be given of by DPVBi and rubrene respectively. There are so characteristics because of the design new multi-structure making the efficiency of blue (emission) increased and the property of the device improved obviously. So we consider that the improvement of emission comes from doping of rubrene leading to carrier transporting from Alq_3 to DPVBi.